Section: Information In-depth
Near-drowning is defined as survival for longer than 24 hours following complete submersion in water. Near-drowning occurs in four stages:
Stage 1 – represented by breath-holding and swimming motions
Stage 2 – involves aspiration of water into the lungs, choking and struggling
Stage 3 – characterized by vomiting
Stage 4 – characterized by loss of consciousness, relaxation and death
Salt water and fresh water near-drowning vary in how they affect the lungs. Because of it's high sodium content, salt water draws water from the bloodstream into the airways effectively flooding the airways. Fresh water inactivates a substance called surfactant, which is manufactured by the lungs and functions to keep the lungs from collapsing. Without surfactant, the airways collapse (atelectasis). Therefore, the main feature of salt water drowning is pulmonary edema (fluid in the airways) and the main feature of fresh water drowning is atelectasis (collapse of airways). Fresh water near-drowning carries a better prognosis than salt water near-drowning.
Near-drowning in cold water carries a better prognosis than warm water. Cold water protects the brain from damage due to lack of oxygen by lowering the pet's body temperature, which subsequently decreases the body's demand for oxygen. Cold water can also initiate the diving reflex, which causes a decrease in the pet's heart rate and redirects blood to vital organs such as the brain and heart to delay brain damage.
Laryngospasm, spasm and closure of the airway occurs in approximately 10 percent of near-drowning victims and results in asphyxia, which is a total lack of oxygen. Laryngospasm minimizes damage to the lungs by preventing water from entering the airways. However, unless the laryngospasm is relieved, your pet will die from lack of oxygen.
Aspiration of water into the lungs causes the lungs to lose their elasticity and become stiff, which makes it more difficult to breathe. Pulmonary edema, an accumulation of water in the lungs, occurs if your pet directly aspirates the water into the lungs. However, it can also result from struggling to breathe against a closed airway as in laryngospasm or secondary to hypoxic (no oxygen) brain damage and is termed neurogenic pulmonary edema.
Cerebral edema, swelling of the brain, can occur secondary to loss of oxygen. If cerebral edema is severe, the pet may experience seizures, loss of consciousness, coma and death. Arrhythmias, or abnormal heart rhythms, may occur as a result of near-drowning and shock.
